Halbtöne

Halbtöne, in English semitones, denote the interval of one half step—the smallest interval used in most Western tonal music. The term comes from Halb (half) and Ton (tone). In the standard octave, twelve Halbtöne comprise the chromatic scale and form the basis of equal-tempered tuning.

In traditional music theory there are two types of semitones. The diatonischer Halbton (diatonic semitone) occurs between two adjacent scale degrees within a diatonic scale, for example E–F or B–C in C major. The chromatischer Halbton (chromatic semitone) occurs between notes of the same letter name when altered by accidentals, such as C–C♯ or E–E♭. These distinctions matter for historical tunings and some voice-leading concepts, even though modern practice often treats all semitones equally in equal temperament.

In equal temperament, which dominates contemporary Western music, all Halbtöne are of equal size: 100 cents, corresponding to the frequency ratio the twelfth root of 2. Historically, other tuning systems such as meantone or well temperament varied the sizes of diatonic and chromatic semitones, affecting keys and harmony differently.

Halbtöne are central to melody, harmony, and modulation, defining scales, chords, and intervallic relationships. While the concept is most closely associated with Western classical and popular music, it also appears in adjacent musical cultures and in discussions of intonation and microtonality.